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A compact probe for charged particle imaging, with potential applications in source activity mapping and radio-guided surgery was designed and tested. The development of this technology holds significant implications for medical imaging, offering healthcare professionals accurate and efficient tools for diagnoses and treatments. To fulfill the portability requirements of these applications, the probe was designed for battery operation and wireless communication with a PC. The core sensor is a dual-layer CMOS SPAD detector, fabricated using 150 nm technology, which uses overlapping cells to produce a coincidence signal and reduce the dark count rate (DCR). The sensor is managed and interfaced with a microcontroller, and custom firmware was developed to facilitate communication with the sensor. The performance of the probe was evaluated by characterizing the on-board SPAD detector in terms of the DCR, and the results were consistent with the characterization measurements taken on the same chip samples using a purposely developed benchtop setup. [ABSTRACT FROM AUTHOR]

Silicon radiation detectors, a special type of microelectronic sensor which plays a crucial role in many applications, are reviewed in this paper, focusing on fabrication aspects. After addressing the basic concepts and the main requirements, the evolution of detector technologies is discussed, which has been mainly driven by the ever-increasing demands for frontier scientific experiments. [ABSTRACT FROM AUTHOR]

A monolithic pixel sensor with high spatial granularity (35 × 40 μm2) is presented, aiming at thermal neutron detection and imaging. The device is made using the CMOS SOIPIX technology, with Deep Reactive-Ion Etching post-processing on the backside to obtain high aspect-ratio cavities that will be filled with neutron converters. This is the first monolithic 3D sensor ever reported. Owing to the microstructured backside, a neutron detection efficiency up to 30% can be achieved with a 10B converter, as estimated by the Geant4 simulations. Each pixel includes circuitry that allows a large dynamic range and energy discrimination and charge-sharing information between neighboring pixels, with a power dissipation of 10 µW per pixel at 1.8 V power supply. The initial results from the experimental characterization of a first test-chip prototype (array of 25 × 25 pixels) in the laboratory are also reported, dealing with functional tests using alpha particles with energy compatible with the reaction products of neutrons with the converter materials, which validate the device design. [ABSTRACT FROM AUTHOR]

Recent advances in segmented low‐gain avalanche detectors (LGADs) make them promising for the position‐sensitive detection of low‐energy X‐ray photons thanks to their internal gain. LGAD microstrip sensors fabricated by Fondazione Bruno Kessler have been investigated using X‐rays with both charge‐integrating and single‐photon‐counting readout chips developed at the Paul Scherrer Institut. In this work it is shown that the charge multiplication occurring in the sensor allows the detection of X‐rays with improved signal‐to‐noise ratio in comparison with standard silicon sensors. The application in the tender X‐ray energy range is demonstrated by the detection of the sulfur Kα and Kβ lines (2.3 and 2.46 keV) in an energy‐dispersive fluorescence spectrometer at the Swiss Light Source. Although further improvements in the segmentation and in the quantum efficiency at low energy are still necessary, this work paves the way for the development of single‐photon‐counting detectors in the soft X‐ray energy range. [ABSTRACT FROM AUTHOR]

The Source Follower (SF) as the first amplification stage of the front-end electronics has proven to be an effective tool for low-noise read-out of silicon radiation sensors. Since the noise properties of a well-designed amplification circuit are mainly determined by its very first stage, constraints on the subsequent electronics are relaxed. Moreover, since the SF is characterized by a low output resistance, once it is completely integrated into the detector substrate, the connections to the out-of-chip part of the circuit are also relaxed. The effectiveness of this solution and the overall performance of the system depend on the sensor properties. In this paper, by presenting analytical calculations and measurements, we identify the sensor types that could profit from the advantages provided by the integrated SF, and the devices where the SF shows some pitfalls. Although the results presented in this paper have been obtained with an integrated JFET technology, the conclusions are valid for whatever technology the SF is made. [ABSTRACT FROM AUTHOR]

We present new results on the influence of radiation-induced damage on the electron Impact Ionization (I.I.) coefficient \alpha, suggesting a small but distinct reduction of \alpha at high fluence with respect to unirradiated silicon. Experiments on thick (1.5 \mum) and thin (1 \mum) epitaxial silicon samples confirm that such a reduction of \alpha is expected even in cases where impact ionization is not simply a field driven process because of strongly non local transport conditions. [ABSTRACT FROM AUTHOR]

The planned luminosity upgrade of the CERN LHC to the super LHC (sLHC) requires investigation of new radiation hard tracking detectors. Compared to the LHC, tracking detectors must withstand a 5–10 times higher radiation fluence. Promising radiation hard options are planar silicon detectors with n-side readout and silicon detectors in 3D technology, where columnar electrodes are etched into the silicon substrate. This article presents beam test measurements performed with planar and 3D n-in-p silicon strip detectors. The detectors were irradiated to different fluences, where the maximum fluence was 3\times 10^15 1 MeV neutron equivalent particles per square centimeter (neq/\rm cm^2) for the planar detectors and 2\times 10^15~neq/\rm cm^2 for the 3D detectors. In addition to signal measurements, charge sharing and resolution of both detector technologies are compared. An increased signal from the irradiated 3D detectors at high bias voltages compared to the signal from the unirradiated detector indicates that charge multiplication effects occur in the 3D detectors. At a bias voltage of 260 V, the 3D detector irradiated to 2\times 10^15~neq/\rm cm^2 yields a signal almost twice as high as the signal of the unirradiated detector. Only 30% of the signal of an unirradiated detector could be measured with the planar detector irradiated to 3\times 10^15~neq/\rm cm^2 at a bias voltage of 600 V, which was the highest bias voltage applied to this sensor. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we report on the design, fabrication, electrical and optical characterization of innovative silicon npn bipolar junction phototransistors, with a finger-shaped emitter implant. Different finger width and interfinger distances, emitter geometries, metal contacts and doping profiles have been implemented to study the impact on the current gain and the spectral responsivity. Such a finger emitter/base junction proved to significantly enhance both the current gain and the responsivity in the blue spectral region with respect to the standard fully implanted detector (maximum current gain of 158 and 72, and responsivity=0.25 and 0.20A/W, respectively). BJTs featuring an additional N-channel implant below the emitter n+-fingers were also successively fabricated and exhibit an improved current gain of 650. The comparison of experimental results for all the implemented geometries allow the identification of the best performing BJT, in terms of current gain and responsivity, and of a figure of merit which takes into account the two fundamental layout parameters affecting the optical and electrical performance: number of emitter fingers and their total perimeter. The new finger-BJTs will be employed as gas sensors after being coated with a metalloporphyrin sensing film, that changes its light absorption properties in the blue when interacting with the gas molecules. A functional measurement campaign has been scheduled with ethanol vapors at different concentrations. [Copyright &y& Elsevier]

Due to their low depletion voltage, even after high particle fluences, improved tracking precision and momentum resolution, and reduced material budget, thin substrates are one of the possible choices to provide radiation hard detectors for future high energy physics experiments. In the framework of the CERN RD50 Collaboration, we have developed PIN diode detectors on membranes obtained by locally thinning the silicon substrate by means of TMAH etching from the wafer backside. Diodes of different shapes and sizes have been fabricated on 50-μm and 100-μm thick membranes and tested, showing a low leakage current (of 300 nA/cm³) and a very low depletion voltage (in the order of 1 V for the 50 μpm membrane) before irradiation. Radiation damage tests have been performed with 58 MeV lithium (Li) ions up to the fluence of 1014 Li/cm² in order to determine the depletion voltage and leakage current density increase after irradiation. Charge collection efficiency tests carried out with a β- particle source have been performed on both nonirradiated devices and samples irradiated upto 1.8 × 1013 Li/cm². Results reported here confirm the advantages of thinned diodes with respect to standard 300-μm thick devices in terms of low depletion voltage and high charge collection efficiency. [ABSTRACT FROM AUTHOR]

We report on the electrical behavior of termination structures for silicon diodes irradiated with high-energy particles. In particular, the analysis is focused on samples featuring an all-P-type (APT) termination structure that has already been proved to yield excellent long-term stability performance. The radiation hardness of these structures is compared to that of more common reference devices. In order to characterize various radiation conditions, tests were performed using protons, neutrons, and high-energy electrons with different influences up to values causing substrate type inversion. We verified that the APT samples remain functional in all the considered situations, their operational limit being comparable to that of the other devices. [ABSTRACT FROM AUTHOR]

Focuses on a specially tailored fabrication technology aimed at the fabrication of silicon microstrip detectors with integrated front-end electronics. Uses of the technology; Characteristics of the fabrication process; Benefits from integrating radiation detectors; Suitability of a monolithic approach.

Proposes a compact, analytical model for the ohmic-side interstrip resistance of double-sided silicon microstrip detectors. Model concept, model equations and model parameters; Validation of the model concept and model outcomes; Implications for metal-oxide-silicon field-effect transistors.

The paper presents the simulation studies of 10 μ m pitch microstrips on a fully depleted monolithic active CMOS technology and describes their potential to provide a new and cost-effective solution for particle tracking and timing applications. The Fully Depleted Monolithic Active Microstrip Sensors (FD-MAMS) described in this work, which are developed within the framework of the ARCADIA project, are compliant with commercial CMOS fabrication processes. A set of Technology Computer-Aided Design (TCAD) parametric simulations was performed in the perspective of an upcoming engineering production run with the aim of designing FD-MAMS, studying their electrical characteristics, and optimizing the sensor layout for enhanced performance in terms of low capacitance, fast charge collection, and low-power operation. A fine pitch of 10 μ m was chosen to provide high spatial resolution. This small pitch still allows readout electronics to be monolithically integrated in the inter-strip regions, enabling the segmentation of long strips and the implementation of distributed readout architectures. The effects of surface radiation damage expected for total ionizing doses of the order of 10 to 10 5 krad were also modeled in the simulations. The results of the simulations exhibit promising performance in terms of timing and low power consumption and motivate R&D efforts to further develop FD-MAMS; the results will be experimentally verified through measurements on the test structures that will be available from mid-2021. [ABSTRACT FROM AUTHOR]

Abstract: We present a new 3D detector architecture aimed at simplifying the manufacturing process making it more suitable for high volume production. In particular, the proposed device features electrodes of one doping type only, e.g., columns in a p-type substrate. We report on TCAD simulation results providing deep insight into the static and dynamic behavior of this detector, highlighting its advantages and potential drawbacks. The fabrication process we intend to use is also described along with results from the morphological characterization of the most critical technological steps. [Copyright &y& Elsevier]

Thin substrates are one of the possible choices to provide radiation hard detectors for future high-energy physics experiments. Among the advantages of thin detectors are the low full depletion voltage, even after high particle fluences, the improvement of the tracking precision and momentum resolution and the reduced material budget.In the framework of the CERN RD50 Collaboration, we have developed p–n diode detectors on membranes obtained by locally thinning the silicon substrate by means of tetra-methyl ammonium hydroxide etching from the wafer backside. Diodes of different shapes and sizes have been fabricated on 57 and 99 μm thick membranes. They have been tested, showing a very low leakage current (<0.4 nA/cm2) and, as expected, a very low depletion voltage (<1 V for the 57 μm membrane). The paper describes the technological approach used for devices fabrication and reports selected results from the electrical characterization. [Copyright &y& Elsevier]

Abstract The INFN CSN5 "TIMESPOT" project aims at the development and implementation of a complete integrated tracking system featuring very high precision both in space and in time for every pixel. Within this framework we are developing 3D pixel sensors optimized for timing, while retaining their usual advantages of low depletion voltage, extreme radiation hardness, and active edges. The pixel geometries are being optimized in terms of size, electrode configuration and shape. In particular, trenched electrodes are used instead of columns, so as to achieve more uniform electric and weighting field profiles. No established technology exists for 3D sensors with trenched electrodes, so we have developed and tested the necessary process steps. In this paper we report the main design and fabrication issues and selected results from TCAD simulations. Highlights • We report on 3D pixel sensors with trenched electrodes optimized for timing. • We thoroughly discussed the design and technological aspects. • We studied with TCAD the trade-off between intrinsic speed and pixel capacitance. • We demonstrated the technological feasibility of the proposed geometries. [ABSTRACT FROM AUTHOR]

Abstract: Recently, we presented a new 3D detector architecture aimed at simplifying the manufacturing process, making it more suitable for high-volume production. In particular, the proposed device features electrodes of one doping type only, e.g., n+ columns in a p-type substrate. In this paper we report on the fabrication at ITC-irst of the first batch of prototypes. The main issues related to the fabrication process along with preliminary results from the electrical characterization of different detectors and test structures are discussed. [Copyright &y& Elsevier]

Abstract: The 3D silicon radiation detectors are very promising devices to be used in environments requiring extreme radiation hardness, such as the super-LHC experiment at CERN. A drawback of this detector is the very long and non-standard fabrication process, which makes the mass production of these devices very critical. A possible simplification of the manufacturing process relies on a new type of 3D architecture, called 3D-single-type-column detector, that we have introduced in previous works. In this paper we report on the fabrication process of the first batch of detectors and on selected results from the electrical characterization of 3D test structures, covering leakage current, capacitance and breakdown voltage measurements. [Copyright &y& Elsevier]

Abstract: Prototypes of ionizing radiation detectors with internal signal amplification based on the bipolar transistor effect have been fabricated at ITC-irst (Trento, Italy). Results from the electrical characterization and preliminary functional tests of the devices have been previously reported. Here, we present a more detailed investigation of the performance of this type of detector, with particular attention to their noise and rate limits. Measurements of the signal waveform and of the gain versus frequency dependence are performed by illuminating the devices with, respectively, pulsed or sinusoidally modulated IR light. Pulse height spectra of X-rays from an source have been taken with very simple front-end electronics (an LF351 operational amplifier) or by directly reading with an oscilloscope the voltage drop across a load resistor connected to the emitter. An equivalent noise charge (referred to input) of 380 electrons r.m.s. has been obtained with the first setup for a small device, with an active area of and a depleted thickness of 0.6mm. The corresponding power dissipation in the BJT was . The performance limitations of the devices are discussed. [Copyright &y& Elsevier]

Abstract: We report on the results from the production of 600 double-sided silicon microstrip detectors for the ALICE experiment. We present the fabrication process and some selected results from the electrical characterization of detectors and test structures. The large amount of experimental data allowed a statistically relevant analysis to be performed. The main technological aspects related to production yield optimization will also be addressed. [Copyright &y& Elsevier]

Looking forward to future High Luminosity LHC experiments, efforts to develop new tracking detectors are increasing. A common approach to improve track reconstruction efficiency in high pile-up conditions is to add time measurement per pixel with resolution smaller than 50 ps. Different sensor technologies are under development in order to achieve those performances, like low gain avalanche diodes and 3D sensors. 3D sensors are characterized by very fast charge collection times, but present some critical issues in timing due to their electrode configurations. The presence of zero electric field volumes inside the electrodes themselves and low electric field regions between same sign electrodes causes that the 3D sensor technology presents potentially a large time walk contribution which negatively affects time resolution. In order to reduce this error drastically, a detailed study based mostly on simulation has been done with main focus on the exploration for a timing optimized 3D sensor electrode configuration. To have a more detailed view of the timing performances, sensor operation was also simulated, using TCAD and other simulation tools developed specific for this application, and the results analysed. In this presentation a detailed overview of the modelling and simulation activity as well as their results, including also future steps will be presented. The output of this studies defines the optimal sensor layout for timing applications. [ABSTRACT FROM AUTHOR]